Erwin Osiel REYNA LOPEZ

Numerical Simulation of Deterioration Process of Concrete Structures of  Electric Power Facilities due to Chloride Attak

Takumi SHIMOMURA

Recent inspections of underground service tunnels have revealed significant deterioration, including cracks, concrete spalling, and steel reinforcement corrosion. Investigations have confirmed high chloride content in the concrete walls of these facilities. Multiple tunnels exhibit similar deterioration, making it essential to clarify the deterioration mechanism. Therefore, this study aims to investigate the deterioration mechanism of reinforced concrete structures in electric power facilities through numerical simulation.
As part of this research, a case study was conducted on the Toyosu service tunnel in Tokyo, which connects the Shin-Toyosu and Shin-Keiyo substations. A technical inspection in July 2024 revealed significant localized damage near the drainage system, particularly in the lower sections, where moisture infiltration marks were observed, indicating water accumulation in this zone. Laboratory analyses of concrete samples collected in 2019 and 2024 confirmed high chloride ion concentrations, reinforcing concerns about structural degradation. Using inverse calculation methods, this study estimates that the tunnel was exposed to external water infiltration for approximately one year, with a chloride concentration equivalent to a 9%-10% NaCl solution.
Numerical simulations indicate that capillary suction was the primary transport mechanism for chloride ions, leading to deep penetration into the concrete. The model successfully replicated the chloride ion concentration profiles observed in the 2019 inspection, confirming the accuracy of the predictive approach. However, this concentration significantly exceeds typical seawater levels, raising concerns about how the accumulated water in the tunnel reached such high chloride concentrations. Therefore, additional research is needed to determine whether this resulted from a single event or recurrent infiltration episodes over time.
Future studies should refine the numerical model by integrating chloride transport mechanisms under alternating moisture and drying conditions. Enhancing the model’s predictive accuracy will provide deeper insights into environmental influences on chloride penetration and diffusion in reinforced concrete structures.